Humidity responsive device



4 Sheets-Sheet l INVENTORS Walter E. Windsor Andrew I IQDLL.

BY ME 6%6/ ATTORNEY W. E. WINDSOR ET AL HUMIDITY RESPONSIVE DEVICE Sept. 15, 1953 Filed Jan. 20, 1950 Sept. 15, 1953 w. E. WINDSOR ET AL HUMIDITY RESPONSIVE DEVICE 4 Sheets-Sheet 2 Filed Jan. 20, 1950 INVENTORS Walter 'Elvindsbf" I v KOlL.

ATTORNEY Sept. 15, 1953 Filed Jan. 20, 1950 W. E. WINDSOR ET AL HUMIDITY RES PONSIVEZ DEVICE 4 Sheets-Sheet 5 INVENTORS Wall'er E. Wirzdsor Andrew J. KolL.

BY ma 6% ATTORNEY P 1953 w. E. WINDSOR ET AL 2,651,941

HUMIDITY RESPONSIVE DEVICE Filed Jan. 20', 1950 4 Sheets-Sheet 4 .a ki

u g V 41 INVENTORS Wali'er E. Windsor Andrew .T. Koll.

ATTORNEY Patented Sept. 15, 1953 HUMIDITY RESPONSIVE DEVICE Walter E. Windsor, Essex, and Andrew J. Koll, Baltimore, Md., assignors to Bendix Aviation Corporation, Baltimore, Md., a corporation of Delaware Application January 20, 1950, Serial No. 139,678

4 Claims.

This invention relatesgenerally to improvements in humidity responsive devices, and particularly to improvements of such a nature that achieve a compact, rugged, low-cost instrument without sacrificing precise operation.

In humidity responsive devices utilizing human hair as the hygroscopic element, it is a wellknown fact that the motion developed by the expansion or contraction of the hygroscopic element is non-linear throughout the range of humidity; thus, ordinary hair elements will undergo fifty percent of their total extension when the relative humidity is approximately thirty-five percent. The other fifty percent total extension takes place in the range of thirty-five to one hundred percent relative humidity and, obviously, such a characteristic motionis non-linear. If the hair element is to be incorporated into a device that is used as an indicator, it is desirable that some means be provided to convert the nonlinear motion derived from the hair element into a linear motion of the indicator arm so that same can be used with a linear scale. Of course, it would be possible to use a non-linear scale and couple the indicating arm directly to the hair element. Such an arrangement isunsatisfactory, though, for portions of the scale will be crowded, whereas portions of the scale will be expanded and an observer will experience difiiculty in using and reading the instrument. It is highly desir- Q able to have a linear scale for maximum ease of sion into an output indication; This contributes to greater accuracy in that inaccuracies inherent in the hair element are magnified by any motion magnifying linkage systemused, and if the motion magnification is kept to, a minimum, resulting errors will be kept to a minimum. For this reason, it is desirable to utilize thegreatest length I of hair so that the extension of the hair element is at a maximum. By using the greatest possible hair length, a larger scale may be used without necessity of resorting to complicated motion magnifying linkage systems; a

' With theaboveinimind, it becomes a problem to properly utilize-the maximum length hair ele- 2 ments in a compact instrument having dimensions on the order of 4 x 5%" x 1%. Some means must be provided to suitably arrange a maximum length of hair within the compact housing so that the benefits resulting from the maximum length hair can be obtained.

In all humidity responsive devices utilizing human hair, the problem of calibration is extremely important, in that individual hairs will vary as to their characteristics. Further, if low manufacturing cost is to be achieved, dimensional tolerances must be rather loose and this adds to the calibration problem. Therefore,

some means must be provided to easily and accurately calibrate the device upon the completio of the assembly thereof. I

Accordingly, it is an object of the present invention to provide a novel humidity indicator utilizing human hair as the hygroscopic element, wherein a maximum length of human hair is used, simple and eifective means are provided to convert the non-linear motion of the hair elements into linear motion of an indicating arm, simple and accurate means are provided to calibrate the instrument, and the entire combination is confined in a small, compact housing.

The invention comprises an elongated hair element looped around a roller aflixed to one side of the instrument housing so that the extremities of the hair element-extend to the opposite side of the instrument housing; thus, permitting the use of a hair element having a length substantially twice the overall length ofthe instrument. One end of thehair element is afiixed to a rather stiff flexible member which operates as a combined support and overload strain relief. The flexible member is relatively adjustable so that a zero-setting of the instrument can be accomplished. The other end of the hair element is adjustably secured to one end of a pivoted bell crank, to the other end of which is adjustably secured a non-hygroscopic filament. The filament extends from the crank, passes over a cam surface and is affixed thereto. The cam surface is pivotally mounted, and there is affixed thereto an indicator arm. A suitable spring is provided to maintain the system in tension. The cam surface has a configuration which converts the nonlinear extension of the hair element into a linear motion of its associatedindicator arm. The adjustableconnection between the hair element and the crank is a so-called rangin adjustment to compensatefor variations in hair extension, and

so that individual variations in filament length can be corrected, from unit to unit.

A detailed description now follows, which, when taken in conjunction with the drawings annexed hereto, will suitably outline the mode of construction, operation, and method of calibration of the novel'instrument disclosed'herein.

In the'drawings:

Fig. l is a front view of the instrument with the front portion of the housing cut away.

Fig. 2 is a bottom view of the instrument with the bottom portion of the housing removed.

Fig. 3 is an end view ofithednstrument with the end portion of the housing cut a'way. V

Fig. 4 is an exploded view show-ing the man-. ner in which the cam and its associated indicator arm are assembled. V

Fig. 5 is a side view of the view shown in Fig. 4.

Fig. 6 is an explodedview of the crank shown inflilig. 1.

Figs. "7 '-and"8'-.-'are: other views of the crank :shown in Fig; 6.

.-Referring first to Figs. 2-and 3, it isseenthat the instrument comprises a. housing I I having a detachable-back plateflrto which'may be secured-:a supportingipanebfi. The. panel Iii-carries the associated. condition responsive elements, linkagesystemi-and indicator arm in cooperaation with front panel'M. The-two-panelsi'a and I4 may besuitablysecured together in spaced .r'elationship bymeans of: spacer members I 5 and cooperating .bolts I6. Both extremities of each -spacermember-l5 are of a reduced diameter to :aifordshouldersabutting against the inner opposite faces of panels 'I- 3, .I,4,: and-neck portions extending into cooperating apertures located in the. panels 13, I I. The neckportions cooperating -withpanel I4 extendbeyond the panel and have their peripheral edges rolled over to provide a tightclamping action. The neck portions cocoperatingwith; panel I3 do not extendbeyond -the-.pane1,;but theyhave threaded bores to cooperateswith threaded bolts I6. One pair of the bolts -I6 abut the rear face of panel I3, whereas the other pair are elongated so 7 as to permit the boltstoabut 'the rear face of plate l2. 'A pair .of. suitableauxiliary spacer members I! are provided-between the plate I2 and panel I 3 through which,-the elongated pair of bblts 'IG extend. Ihus, the spacers I5 and I! an'dbolts it serve to clamp the panel together and to the back iplataan'd maintainsame inproperly spaced rellationship.

lThe back plate I 2 isse'cured to-theihousing a: J

.by means of .a "pair of screws I8, which pass through apertures'in the plate I2 and cooperate with threadedapertures in the brackets l9 rig- .idlyfast'en'ed to the housing I I.

The panel I3hasa pair of supporting brackets '2I, 22, extending substantially at right angles 'from' its inner surface" and these bracket mem- "bers2l, 22,may' be formed-bycutting away-sec- '-tions of the panel I3 and bending same upwardly to form-an -approximate right angle. The relatively stifi flexible member 23*has one end hooked around the 'bracket '22 and is rigidly secured thereto by means of rivet M. The Latherend of -'member 23 extends :beyond the bracket '2 I and has its 'outer extremityibent inthe'formof a rest: againststhe projecting :end. of the adjusting 4 screw 25. The screw 25 may be moved with respect to the bracket 2I and this will permit the flexible member 23 to shift its position.

Extending from the turned-over end of flexible member 23 is a small supporting bracket 26. This bracket may be formed by cutting away a section 'of' theflexible member-223mm :bending it upwardly at '-.an approximate right; angle. The supporting bracket 26 afi'ords a relatively fixed .support for one end of a hygroscopic element.

Apulley 21in the form of a cylindrical roller is suitablyjournaled for rotation between the :28 .throughxwhich. passes a pin shaft 29. epinYshaftiLZS' extends through a pair of dimpled panels I:3; I4; .The'gpulley 21 has an axial bore The apertures in thepanels I3, I4, and the end of the pin shaftis flattened so that the shaft is retained in place. "The'inner extremities of the dimpled apertures abut against opposite ends of the pulley 21 to maintain the pulley properly spaced from each panel. The pulleyll has .a serie of parallel grooves 3 I surrounding. its periphery.

Also journaled for rotation between the panels l3, I4,-isa bell.crank 32;the journalmg'arrange- 7 ment being identical to that described for l the pulley 21, there being va ipin .shaftl33 ,passing through 1 the bell lcrank Ii 32, "about which same pivots. Figs. 6; 'lgf ilshowthe 'detailedcorifig'uration of the bell crank-. 32 andit'is to'Tbe. noted that the bottom. section of the bell Icr'ankT is. in

. the form of a-Ue-br acketjl. "'rhe..pin.'shart"aa extends through opposite? legssof the .KU -bracket 34. A- threadedapertureis provided in the'con- 1 nectin g link 35 .of. theiU wrecker and receives therein an. adjustable screw 36,. "The screw "36 provides a relatively movable support for'f'o'ne end of a hygroscopic element;

The hygroscopic times .31 "151 thefo'r'miiof a conventionali'ba'njo.assembly'of parallel spaced elongated human hairs having their ends clamped together' by' mea'ns of suitable clainps"3B,"the clamps -38'being adapted'to engagethe bracket support 26 andithe' adjustablescrew 38. The

" hygroscopic element"3'Ifpas'sesfover'the pansy-21 and the Individual hair elementsresti'in"the grooves 3 I, provided the,'periphe ry .of'pulleyfzl.

i crank "32 .we see'that' the" upperendofthe' hell i crank has afiixed' thereto; ,near'"its'extremityfthe auxiliary crank 9. "T'I'heauxiliary crank is pivauxiliary crank 39have cooperating s'ections-"42, "43, extending approximately at 'rightangles to their, surfaces. The'section 42 has a" threaded aperture'f or 'receiving'jtherein' the adj usting'screw '14. The .en'd'ofgthe adjusting "screw-4'4 rests :against the fsection "'43. -Rigidly"secured 'as *by Way of 'a'rivet to the upper-end o'f auxiliarycra'nk 'crank' 32- there "between; the pan I shaft-4 Bj-of the type heretofore describedin con- Situated belowthe upper "-'extremlty of 'th e bell a'cam' ll journaled for=rotaticn ream illby 'means of a pin 1 nection'withthe journalin'garrangements ofthe :mummies:were i219; Fi s m be referre'd'to "in cfq'nnec'tion with -the following description. Thecamiilhashm active cam surface 49fan'd'an inactivesubstantlallyfiat surface -41 isan indicator arm 54 having its respective ends offset from one another and having one end rigidly secured to one of the plates by means of rivets or the like. A spacer member 55 surrounds the pin shaft 48 and extends between the panel [4 and one face of the indicator arm 54. This spacer serves to maintain the cam--4'I and its associated structure properly spaced between the panels 13 and l4. The extremityof the arm 54 away from the cam 41 extends through an arcuate slot 56 provided. in the panel 14. This extremity is adaptedto cooperate with a scale (not shown) which may besuitably arrangedon the panel H. A small supporting bracket 51 is stamped out of the arm 54 and cooperates with a small bracket 58 stamped out of panel I3 to provide supports for a relatively weak coil spring 59. i

A non-hygroseopicfilament 6|, which may be glass fibre or the like, is loopedaround the pulley 45, passes over the pulley 46, over the active cam surface 49, and has its ends looped around the pin 52 and is secured thereto.

With the above relationship ofthe component parts in mind, it is apparent that any expansion or contraction of the hygroscopic element 31 will cause the bell crank 32 to rotate about its pin shaft 33. This will cause the upper extremity of the bell crank to rotate about the pin shaft 33 and this rotation will be transmitted to the cam 41 by means of the filament 6|. Any rotation of cam 41 will cause the arm 54 to correspondingly rotate. Thus we see that the arm 54 will move to give an output indication corresponding to changes in length of the hygroscopic element 31.

It is to be noted that the configuration oi the active cam surface 43, is such as to vary the effective lever-arm developed by the filament 6| acting upon the cam 41. In the range of extremely 10w humidities, where the arm 54 is in its extreme left position (see Fig.1), it is to be noted that the effective lever-arm developed by filament 6! is at a maximum. As the arm 54 swings to the righhthe effective lever-arm asserted by filament 6! is gradually reduced to a minimum. Thus, for equal movement of arm 54, a greater motion or extension of the hygroscopic element 3131s, required in the region of low humidity than is required in the region of high humidity. This corresponds to the characteristic of the hygroscopic element 31 in that its greatest relative change of length takes place in the relatively low humidity region and gradually diminishes as saturation is reached. The effect of the above is to produce a linear motion of the arm 54 with changes of humidity. That is to say, equal changes of relative humidity will produce correspondingly equal changes of motion of the arm 54. This arrangement permits the use of a linear scale to cooperate with the arm 54 to give a visual indication of the magnitude of humidity under observation.

The adjusting screws 25, 36, and 44, are provided to calibrate the instrument after assembly, and the manner of calibration will now be described. Ordinarily, in the assembly of the instrument, the adjusting screws 25, 36, and 44 are positioned so that the threaded apertures cooperating with same bisect their threaded portions. With such an arrangement, if all of the parts making up the assembly are fabricated to precise specifications, very little calibration or adjustment will be necessary. However, as is usual in normal manufacturing operations, the parts will vary within specified tolerances and individual calibration of each instrument will be necessary .U-bracket 34 will be substantially parallel to the vertical edges of the panel l3. Knowing this relationship, the first step in calibrating the completed instrument is to artificially position. the bell crank 32 in such a manner as to achieve the aforesaid parallel relationship. This will. correspond, as said before, to fifty percent extension of the hair element 31. Such an extension corresponds to approximately 35 percent relative humidity. Therefore, with the bell crank held in a fifty percent extension position, the adjusting screw 44 is manipulated until the indicator arm reads thirty-five percent relative humidity. This initial adjustment matches the linearizing effect of the cam to the hair element and has the eifect of adjusting the individual instruments for any variations from unit to unit in the length of the filament 6|.

The instrument is next placed in an atmosphere of fifty percent relative humidity and allowed to stabilize for a sufficient period of time. The adjusting screw 25 is then manipulated until the indicator arm 54 reads fifty percent relative humidity. The adjustment of screw 25 :has the effect of shifting the scale of the instrument and, for this reason, is conventionally known as a zero-setting adjustment. Adjustment of screw 25 normally compensates for variations in length between individual hair element assemblies; that is to say, variations in length from unit to unit in the hygroscopic element 31.

The instrument is next placed in an atmosphere of thirty percent relative humidity and allowed to stabilize for a sufficient length of time. The exact indication of the arm 54 is then noted. The instrument is then placed in an atmosphere of seventy percent relative humidity and the exact indication of the arm 54 is noted. If the range in humidity indicated by a reading of the instrument is greater than or less than the actual range, the screw 36 is manipulated to change the magnification of the linkage system. This is effected by changing the position of the hygroscopic element 31 with respect to the pin shaft 33. That is to say, the lever arm, defined by the connection of the hygroscopic element 31 to screw 36 and the fulcrum of the bell crank 32, is varied. Such an adjustment of the screw 36 is called a ranging adjustment and normally v compensatesfor variations inelongation between different hair element assemblies; that is, dif ferences from unit to unit in elongation of the hygroscopic element 31. In this last step in the calibration procedure, if the indicated difference in humidity equals the actual difierenoe but the scale readings do not coincide with actual, the screw 44 is manipulated to move the indicator arm 54 to its correct position.

After the calibration has been completed, the instrument is ready for use, and should function accurately without need for further adjustment under normal conditions.

It is to be noted that the total length of the hygroscopic element 31 is substantially twice the maximum length of the instrument itself. This is achieved by the use of the pulley 2! and results in relatively large total motion from the condition responsive element, thus reducing the magnification required by the linkage system coupling the hygroscopic element to the indicator arm.

zegeumi i'Nearlyzailtith'e partsfmaiiingmpttherassembly can be fabricated by simple sheeti-metalzoperantionsiand cani'be fabricated toz=-natherzioose dimensional ltolerances. "cT-heenevel varra-ngement 01*- the threecal ibratings'crewsili, 3B4and-Z4lper- -mits any looseLtolerances -tozbeucompensated--for after assembly to produce an instrumentathatis :'capable of :giving -accurate i indications mover 1a -sustained period :of operation. The ex ziecteid ac- -curacy "from the instrument -is appr x t y plus or minus flve-pereent. -All of-:the -parts-re quiredfor: adjustment and calibration areereadily -accessible andeasy to menipulateg-and the calibration: procedure is' 'simpltfled-by' the -nev;'e1 i invention. 4

The parts are -assembled within -theaavailable spacein an efficienbmanner-whereby a compact and 'rugged assembly is a'chieved. It is also to be noted that the provision *of --assembling-the panels 1 3, "tOft/h back plate i2 permitsthe'ent-ire assembly tobeea's'fl-y'remmedfrom the hous- -i-ngfor inspection an'd adjustment sis-required.

A series of openings 62 are -provided=i-nflthe sides-and -bottom-'-of -the housingfil'to permit wample flow of airi over the hygroscopic element #31. These openings are covered by suitable screening 63' -toprevent dust, dirt, and -inseets ffrom entering the interior of the "housing. A window *arrangement M- is -a-lso provided in the front face of t-he -housing I I to permit" ready-in- ;spection -of the indicating arm and cooperating scale.

What is claimed ariddesired-to 'besecuredby United- States" Letters Patent is:

" 1. In ahumiditmndicator; in combination A pair of substantially flat rectangularjuxtaposed 'isuppoi'ting platesrigidly'held together; in spaced relation'shipfia;"relatively stiff *flexible memb er 'exten'dingrupwardly between" said plates Wherefby its-upper extremity' is positioned near i Ql'leLrQf -the- 1pper1corners ofisaid 1 plates; means for se- -curingthe 'loweriextremity. of 'saidfflexible mem- '-ber-to one of "said plates," a first screw. adj ust- -ablymounted on-me-of said plates cooperating witlr'said flexible member to change theposition i8 pl'votail-y nibuntedhbetween=said-plates .and ha'viiin'geits lowerileg extending aiownwardl-yitowards theiother lower corner of saidaplates: and its-upper ileg. aextendingzitowards the opposite upper {35 ocorner of said zplatesea secondlscrew carried by thersaid lowerfilegzandzadjustable towary the ef fective leverarm enema 10wer"-1eg, said hygroscopicielement being loopedwaround: said' pulley and i having 1 eme -end =-secured 1, to the upper ex- 10 -tremitysof said fiexible memben and the other aend secured tofi said secondiscrew a second bell crank pivotally monntedmn theupper leg of said first :aben crank,- a -third=srew-earried :by said upper leg of sea/id l-first be'll crank cooperating '=with said -second bell crank to move its free :end

with: respect to--said' first: crankg a cam =pivota1ly #mounted' between said plates :a-nd having-an indicator arm integral therewith, a non-hygroscopic glass-fiber fila'ment havingnone end conandthe other end wrapped around -the aactive surface of--said eam andrconnectedthereto, and

spring --means connected -to said indicator arm to J'naintain I the entire" assembly -under tension,

.25 the 'configuration=-of--said active -cam surface being such-that said-indicator arm hasequal'move- --1nents forequakehanges in -humidity.

2. The combination defined in -e1aim 1 wherein said lower leg of-said first' bell crank is paral- 'lel'to the vertiealedge ofsaid plates-atsubstam' tiaily fifty per-cent rela'tive humidity.

3: -'l?he combinatiomdefined by claim 2 where- '-i-n one of said platesihasan 'arcuate slot, said indicator;arm haS an efiSet portion extending L through Qaidslot, -anda --linearaseale is provided on said-plate 'to-cooperateftherew-ith;

NUT-he combination defined-in claim=3 wherein -a;"housing"is provided:forsaid-platesand' their I 'assooia'tedjparts, there beinga window in said 1: 40 housing :beon atingwithz-sai cale, s di "of the"nppenextremityfthereof, an "elongated 'hygroscopic-'- element extending between said plates, said hygr'osc'opic "-element changing "in length i-n 're sp'onse *to "changes in '-humidityand having-a non-linear characteristic whereby equal changes in"humidity-result in-"unequal jchanges t n 1en'gth,-a;"pu-1ley mounted for-rotation between saidplates-neanone ef -the lower corners- {thereof and diametrically disposed -to said: upper ex- 1 tremity of saidfiexible'member, afir'st-bell crank being *rem'ovably-rconnected' to one side of said h gs .1, is

"Number Nuniber I 'JQWAL' TEHEQWINDSOR. 

